The U.S. Treasury Department slapped further sanctions against Iranian Revolutionary Guard Corps (IRGC) on Wednesday, freezing assets of an individual and four companies affiliated with the Corps.

The targeted individual is IRGC General Rostam Qasemi, commander of Khatam al-Anbiya Construction Headquarters, the engineering arm of the IRGC. The Treasury said it's involved in the construction of streets, highways, tunnels, water conveyance projects, agricultural restoration projects, and pipelines.

The companies targeted in the new sanction move are "four companies that are owned or controlled by, or that act on behalf of, Khatam al-Anbiya," according to the Treasury.

The targeted companies include Fater Engineering Institute, Imensazen Consultant Engineers Institute, Makin Institute and Rahab Institute.

Stuart Levey, the Treasury's Under-Secretary for Terrorism and Financial Intelligence, said the IRGC "is hiding behind companies like Khatam al-Anbiya and its affiliates to maintain vital ties to the outside world."

The IRGC and its Qods Force was designated by the State Department in October 2007 for having engaged, or attempted to engage, in proliferation-related activities. At that time, the Treasury froze assets of the IRGC, the Qods Force, and also nine IRGC-affiliated entities, including Khatam al-Anbiya, and five IRGC-affiliated individuals.

The IRGC is believed by the West to be taking the lead in Iran' s nuclear program, and its influence in both politics and economy of Iran has greatly expanded in recent years. The United States accuses the Corps of crushing the opposition protests last year.

U.S. President Barack Obama said on Tuesday that his administration will develop "a significant regime of sanctions" over the next several weeks targeting Iran, as Tehran declared it had started the process of producing 20-percent enriched uranium inside the country.

Iran has been at the center of an international dispute over its nuclear plan. The United States and its Western allies have been accusing Iran of secretly developing nuclear weapons under the disguise of a civilian program. Iran has denied the accusation and stressed its nuclear program is only for peaceful purposes.